Move plugin config to database

[Nutomic]

This would give us more flexibility, and allow for features like plugin configuration via lemmy-ui or a key-value store for plugins. Also see #6164

As removing the plugin settings from lemmy.hjson would be a breaking change its best to do this before the final 1.0 release.

[dessalines]

I wouldn't be opposed, but the main benefit of DB settings, is that they can be live updated. The plugins require local files which I believe are loaded on lemmy startup, so you'd need to restart lemmy anyway.

Plugins could count as "wiring", which is what the lemmy.hjson should contain.

[Nutomic]

Plugins can also be live updated. Have a look at #6164 for more ideas. For example lemmy-ui could show a list of all available plugins which can be installed with a single click. Similar to apps in Nextcloud:

[dessalines]

Ah nice. Yep that'd be ideal.